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• Combining a few shifted streams with ffmpeg - result's expected duration is incorrect

  27 octobre 2019, par galra

  I need to combine a few streams (videos + an audio), all shifted compare to each other and in different lengths, to a file with synchronized streams. Using a dummy case, I found out the following command will create a file with the video shifted by 10sec compare to the audio, playing in full length :

  ffmpeg -i in.mp4 -itsoffset 10 -i in.mp4 -c copy -map 0:1 -map 1:0 -t  out.mp4

  if the -t flag is dismissed, the original length will be kept, and vlc would stop playing and effectively truncate the last 10sec of the video stream. With mkv however it won’t be truncated, and the presented video length increases by 10secs as expected. Also, ffplay won’t truncate the mp4, rather it will play it until the end, but once the original ending timestamp is reached, the timestamp "freezes" and A-V starts gaining (negative) increasing values. ffplay output will be as :

  368.34 A-V: -6.124 fd=  14 aq=    0KB vq=    0KB sq=    0B f=0/0

  also ffprobe will present the original duration :

  Duration: 00:06:08.71, start: 0.000000, bitrate: 304 kb/s

  where it should have been 00:06:18.71. I’m no expert, but I guess that there’s some metadata field in the mp4 container that tells the total duration. Is there a way to update it, or must I convert the files to mkv to avoid the wrong & confusing duration indication ?

• FFMPEG crop video output is black screen, sound is good [on hold]

  11 janvier 2016, par Oum Alaa

  I cropped a video using ffmpeg command line, the output is black screen, the sound is clear and good :

  ffmpeg -i Original.mp4 -t 00:00:29 -vf "crop=634:300:0:60" Done.mp4

  ffmpeg version :

  ffmpeg version 0.8.17-4:0.8.17-0ubuntu0.12.04.1, Copyright (c) 2000-2014 the Libav developers

  built on Mar 16 2015 13:26:50 with gcc 4.6.3

  video information :

  mediainfo '--Inform=Video;%Width%x%Height%' Original.mp4
  
  634x360

  Thanks in advance

• ffmpeg - produces corrupted file

  1er mai 2015, par pomegranate

  I have a mp4 file that I need to convert to avi to run a matlab script on. This script strips the file of any audio, so then I have to merge it back with the audio and then reconvert the avi to mp4. I’m doing this in a number of steps, and am uncertain at which point I’m screwing the commands up... basically, the final mp4 file I create it corrupted and cannot be played in quicktime (though it does work in VLC).

  Here are the steps I am taking :

  1) ffmpeg -i original.mp4 -acodec copy -vcodec copy original.avi
  
     This converts mp4 to avi.
  
  2) ffmpeg -i original.mp4 -acodec copy original.aac
  
     This gets the audio from the mp4.
  
  3) Run matlab script, which produces new-no-sound.avi
  
  4) ffmpeg -i new-no-sound.avi -i original.aac -c:v copy -c:a aac -strict experimental new-with-sound.avi
  
     This merges the old audio with the new avi file
  
  5) ffmpeg -i new-no-sound.avi -c:v libx264 -crf 19 -preset slow -c:a libfaac -b:a 192k -ac 2 final-version.mp4
  
     This converts the new merged file to mp4.

  Here’s the ffmpeg -i from the original.mp4 :

    Metadata:
  
  major_brand     : isom
  
  minor_version   : 512
  
  compatible_brands: isomiso2mp41
  
  encoder         : Lavf54.29.104
  
  Duration: 00:00:01.77, start: 0.000000, bitrate: 9920 kb/s
  
  Stream #0:0(eng): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 9978 kb/s, 59.94 fps, 59.94 tbr, 2997 tbn, 2997 tbc (default)
  
  Metadata:
  
    handler_name    : VideoHandler
  
  Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 52 kb/s (default)
  
  Metadata:
  
    handler_name    : SoundHandler

  And here is it for new-no-sound.avi :

  Input #0, avi, from 'new-no-sound.avi':
  
  Duration: 00:00:02.12, start: 0.000000, bitrate: 1325789 kb/s
  
  Stream #0:0: Video: rawvideo, bgr24, 1280x720, 1336298 kb/s, 59.94 fps, 59.94 tbr, 59.94 tbn, 59.94 tbc

  Finally, here it is for final-version.mp4

  Metadata:
  
  major_brand     : isom
  
  minor_version   : 512
  
  compatible_brands: isomiso2avc1mp41
  
  encoder         : Lavf55.48.100
  
  Duration: 00:00:02.21, start: 0.023220, bitrate: 2117 kb/s
  
  Stream #0:0(und): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv444p, 1280x720, 2108 kb/s, 59.94 fps, 59.94 tbr, 11988 tbn, 119.88 tbc (default)
  
  Metadata:
  
    handler_name    : VideoHandler
  
  Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 43 kb/s (default)
  
  Metadata:
  
    handler_name    : SoundHandler

  Any advice for where I might be going wrong ?